net/netfilter/nf_conntrack_helper.c

   1 /* Helper handling for netfilter. */
   2
   3 /* (C) 1999-2001 Paul `Rusty' Russell
   4  * (C) 2002-2006 Netfilter Core Team <coreteam@netfilter.org>
   5  * (C) 2003,2004 USAGI/WIDE Project <http://www.linux-ipv6.org>
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License version 2 as
   9  * published by the Free Software Foundation.
  10  */
  11
  12 #include <linux/types.h>
  13 #include <linux/netfilter.h>
  14 #include <linux/module.h>
  15 #include <linux/skbuff.h>
  16 #include <linux/vmalloc.h>
  17 #include <linux/stddef.h>
  18 #include <linux/random.h>
  19 #include <linux/err.h>
  20 #include <linux/kernel.h>
  21 #include <linux/netdevice.h>
  22 #include <linux/rculist.h>
  23 #include <linux/rtnetlink.h>
  24
  25 #include <net/netfilter/nf_conntrack.h>
  26 #include <net/netfilter/nf_conntrack_l3proto.h>
  27 #include <net/netfilter/nf_conntrack_l4proto.h>
  28 #include <net/netfilter/nf_conntrack_helper.h>
  29 #include <net/netfilter/nf_conntrack_core.h>
  30 #include <net/netfilter/nf_conntrack_extend.h>
  31
  32 static DEFINE_MUTEX(nf_ct_helper_mutex);
  33 static struct hlist_head *nf_ct_helper_hash __read_mostly;
  34 static unsigned int nf_ct_helper_hsize __read_mostly;
  35 static unsigned int nf_ct_helper_count __read_mostly;
  36
  37
  38 /* Stupid hash, but collision free for the default registrations of the
  39  * helpers currently in the kernel. */
  40 static unsigned int helper_hash(const struct nf_conntrack_tuple *tuple)
  41 {
  42         return (((tuple->src.l3num << 8) | tuple->dst.protonum) ^
  43                 (__force __u16)tuple->src.u.all) % nf_ct_helper_hsize;
  44 }
  45
  46 static struct nf_conntrack_helper *
  47 __nf_ct_helper_find(const struct nf_conntrack_tuple *tuple)
  48 {
  49         struct nf_conntrack_helper *helper;
  50         struct nf_conntrack_tuple_mask mask = { .src.u.all = htons(0xFFFF) };
  51         struct hlist_node *n;
  52         unsigned int h;
  53
  54         if (!nf_ct_helper_count)
  55                 return NULL;
  56
  57         h = helper_hash(tuple);
  58         hlist_for_each_entry_rcu(helper, n, &nf_ct_helper_hash[h], hnode) {
  59                 if (nf_ct_tuple_src_mask_cmp(tuple, &helper->tuple, &mask))
  60                         return helper;
  61         }
  62         return NULL;
  63 }
  64
  65 struct nf_conntrack_helper *
  66 __nf_conntrack_helper_find(const char *name, u16 l3num, u8 protonum)
  67 {
  68         struct nf_conntrack_helper *h;
  69         struct hlist_node *n;
  70         unsigned int i;
  71
  72         for (i = 0; i < nf_ct_helper_hsize; i++) {
  73                 hlist_for_each_entry_rcu(h, n, &nf_ct_helper_hash[i], hnode) {
  74                         if (!strcmp(h->name, name) &&
  75                             h->tuple.src.l3num == l3num &&
  76                             h->tuple.dst.protonum == protonum)
  77                                 return h;
  78                 }
  79         }
  80         return NULL;
  81 }
  82 EXPORT_SYMBOL_GPL(__nf_conntrack_helper_find);
  83
  84 struct nf_conntrack_helper *
  85 nf_conntrack_helper_try_module_get(const char *name, u16 l3num, u8 protonum)
  86 {
  87         struct nf_conntrack_helper *h;
  88
  89         h = __nf_conntrack_helper_find(name, l3num, protonum);
  90 #ifdef CONFIG_MODULES
  91         if (h == NULL) {
  92                 if (request_module("nfct-helper-%s", name) == 0)
  93                         h = __nf_conntrack_helper_find(name, l3num, protonum);
  94         }
  95 #endif
  96         if (h != NULL && !try_module_get(h->me))
  97                 h = NULL;
  98
  99         return h;
 100 }
 101 EXPORT_SYMBOL_GPL(nf_conntrack_helper_try_module_get);
 102
 103 struct nf_conn_help *nf_ct_helper_ext_add(struct nf_conn *ct, gfp_t gfp)
 104 {
 105         struct nf_conn_help *help;
 106
 107         help = nf_ct_ext_add(ct, NF_CT_EXT_HELPER, gfp);
 108         if (help)
 109                 INIT_HLIST_HEAD(&help->expectations);
 110         else
 111                 pr_debug("failed to add helper extension area");
 112         return help;
 113 }
 114 EXPORT_SYMBOL_GPL(nf_ct_helper_ext_add);
 115
 116 int __nf_ct_try_assign_helper(struct nf_conn *ct, struct nf_conn *tmpl,
 117                               gfp_t flags)
 118 {
 119         struct nf_conntrack_helper *helper = NULL;
 120         struct nf_conn_help *help;
 121         int ret = 0;
 122
 123         if (tmpl != NULL) {
 124                 help = nfct_help(tmpl);
 125                 if (help != NULL)
 126                         helper = help->helper;
 127         }
 128
 129         help = nfct_help(ct);
 130         if (helper == NULL)
 131                 helper = __nf_ct_helper_find(&ct->tuplehash[IP_CT_DIR_REPLY].tuple);
 132         if (helper == NULL) {
 133                 if (help)
 134                         rcu_assign_pointer(help->helper, NULL);
 135                 goto out;
 136         }
 137
 138         if (help == NULL) {
 139                 help = nf_ct_helper_ext_add(ct, flags);
 140                 if (help == NULL) {
 141                         ret = -ENOMEM;
 142                         goto out;
 143                 }
 144         } else {
 145                 memset(&help->help, 0, sizeof(help->help));
 146         }
 147
 148         rcu_assign_pointer(help->helper, helper);
 149 out:
 150         return ret;
 151 }
 152 EXPORT_SYMBOL_GPL(__nf_ct_try_assign_helper);
 153
 154 static inline int unhelp(struct nf_conntrack_tuple_hash *i,
 155                          const struct nf_conntrack_helper *me)
 156 {
 157         struct nf_conn *ct = nf_ct_tuplehash_to_ctrack(i);
 158         struct nf_conn_help *help = nfct_help(ct);
 159
 160         if (help && rcu_dereference_protected(
 161                         help->helper,
 162                         lockdep_is_held(&nf_conntrack_lock)
 163                         ) == me) {
 164                 nf_conntrack_event(IPCT_HELPER, ct);
 165                 rcu_assign_pointer(help->helper, NULL);
 166         }
 167         return 0;
 168 }
 169
 170 void nf_ct_helper_destroy(struct nf_conn *ct)
 171 {
 172         struct nf_conn_help *help = nfct_help(ct);
 173         struct nf_conntrack_helper *helper;
 174
 175         if (help) {
 176                 rcu_read_lock();
 177                 helper = rcu_dereference(help->helper);
 178                 if (helper && helper->destroy)
 179                         helper->destroy(ct);
 180                 rcu_read_unlock();
 181         }
 182 }
 183
 184 int nf_conntrack_helper_register(struct nf_conntrack_helper *me)
 185 {
 186         unsigned int h = helper_hash(&me->tuple);
 187
 188         BUG_ON(me->expect_policy == NULL);
 189         BUG_ON(me->expect_class_max >= NF_CT_MAX_EXPECT_CLASSES);
 190         BUG_ON(strlen(me->name) > NF_CT_HELPER_NAME_LEN - 1);
 191
 192         mutex_lock(&nf_ct_helper_mutex);
 193         hlist_add_head_rcu(&me->hnode, &nf_ct_helper_hash[h]);
 194         nf_ct_helper_count++;
 195         mutex_unlock(&nf_ct_helper_mutex);
 196
 197         return 0;
 198 }
 199 EXPORT_SYMBOL_GPL(nf_conntrack_helper_register);
 200
 201 static void __nf_conntrack_helper_unregister(struct nf_conntrack_helper *me,
 202                                              struct net *net)
 203 {
 204         struct nf_conntrack_tuple_hash *h;
 205         struct nf_conntrack_expect *exp;
 206         const struct hlist_node *n, *next;
 207         const struct hlist_nulls_node *nn;
 208         unsigned int i;
 209
 210         /* Get rid of expectations */
 211         for (i = 0; i < nf_ct_expect_hsize; i++) {
 212                 hlist_for_each_entry_safe(exp, n, next,
 213                                           &net->ct.expect_hash[i], hnode) {
 214                         struct nf_conn_help *help = nfct_help(exp->master);
 215                         if ((rcu_dereference_protected(
 216                                         help->helper,
 217                                         lockdep_is_held(&nf_conntrack_lock)
 218                                         ) == me || exp->helper == me) &&
 219                             del_timer(&exp->timeout)) {
 220                                 nf_ct_unlink_expect(exp);
 221                                 nf_ct_expect_put(exp);
 222                         }
 223                 }
 224         }
 225
 226         /* Get rid of expecteds, set helpers to NULL. */
 227         hlist_nulls_for_each_entry(h, nn, &net->ct.unconfirmed, hnnode)
 228                 unhelp(h, me);
 229         for (i = 0; i < net->ct.htable_size; i++) {
 230                 hlist_nulls_for_each_entry(h, nn, &net->ct.hash[i], hnnode)
 231                         unhelp(h, me);
 232         }
 233 }
 234
 235 void nf_conntrack_helper_unregister(struct nf_conntrack_helper *me)
 236 {
 237         struct net *net;
 238
 239         mutex_lock(&nf_ct_helper_mutex);
 240         hlist_del_rcu(&me->hnode);
 241         nf_ct_helper_count--;
 242         mutex_unlock(&nf_ct_helper_mutex);
 243
 244         /* Make sure every nothing is still using the helper unless its a
 245          * connection in the hash.
 246          */
 247         synchronize_rcu();
 248
 249         rtnl_lock();
 250         spin_lock_bh(&nf_conntrack_lock);
 251         for_each_net(net)
 252                 __nf_conntrack_helper_unregister(me, net);
 253         spin_unlock_bh(&nf_conntrack_lock);
 254         rtnl_unlock();
 255 }
 256 EXPORT_SYMBOL_GPL(nf_conntrack_helper_unregister);
 257
 258 static struct nf_ct_ext_type helper_extend __read_mostly = {
 259         .len    = sizeof(struct nf_conn_help),
 260         .align  = __alignof__(struct nf_conn_help),
 261         .id     = NF_CT_EXT_HELPER,
 262 };
 263
 264 int nf_conntrack_helper_init(void)
 265 {
 266         int err;
 267
 268         nf_ct_helper_hsize = 1; /* gets rounded up to use one page */
 269         nf_ct_helper_hash = nf_ct_alloc_hashtable(&nf_ct_helper_hsize, 0);
 270         if (!nf_ct_helper_hash)
 271                 return -ENOMEM;
 272
 273         err = nf_ct_extend_register(&helper_extend);
 274         if (err < 0)
 275                 goto err1;
 276
 277         return 0;
 278
 279 err1:
 280         nf_ct_free_hashtable(nf_ct_helper_hash, nf_ct_helper_hsize);
 281         return err;
 282 }
 283
 284 void nf_conntrack_helper_fini(void)
 285 {
 286         nf_ct_extend_unregister(&helper_extend);
 287         nf_ct_free_hashtable(nf_ct_helper_hash, nf_ct_helper_hsize);
 288 }